1. Field of the Invention
The present invention relates to image processing apparatuses, image processing methods, and computer programs. More specifically, the present invention relates to an image processing apparatus, an image processing method, and a computer program with which scalability is provided so that it is possible to control quality of picture display selectively in accordance with the status of bandwidth of a transmission path, the processing ability of an apparatus, and so forth.
2. Description of the Related Art
In schemes for encoding moving pictures, for example, defined by MPEG (Moving Picture Experts Group), techniques referred to as SNR (signal to noise ratio) scalability and FGS (fine granular scalability) exist. Using these techniques, it is possible to define layers of encoded bitstreams so that a recipient of encoded data can determine the quality of output pictures by selectively decoding data.
SNR scalability techniques are defined in MPEG-2 encoding. According to the techniques, a low-SNR bitstream (base layer) generated by an encoder with a rough quantization size, and extra bitstreams (enhancement layers) generated by small quantization sizes from signals obtained by subtracting base signal components from input signals are transmitted in layers, so that a recipient can obtain a low-SNR picture of a lowest quality by decoding only the base signal in accordance with the status of communications.
FGS techniques are defined in MPEG-4 encoding. According to FGS techniques, it is possible to control SNR more delicately in enhancement layers. According to FGS techniques, DCT (discrete cosine transform) coefficients are bit-plane encoded for transmission, so that it is possible to control picture quality by decoding only high-order bits depending on the transmission bandwidth. The SNR scalability techniques in MPEG-2 and the FGS techniques in MPEG-4 are described, for example, in “Overview of Fine Granularity Scalability in MPEG-4 Video Standard”, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 11, NO. 3, MARCH 2001.